A conventional air-conditioning device for a vehicle seat has a seat, a seat air-conditioning duct, a floor-side connection part, a seat-side connection part, and a connection duct. A position of the seat is adjusted in a front-rear direction of a vehicle. The seat air-conditioning duct guides air that is supplied from an interior air-conditioning unit to a lower side of the seat. The floor-side connection part is disposed on the lower side of the seat that is under an interior floor and connects to the seat air-conditioning duct. The seat connection part is disposed on a seat bottom surface of the seat and connects to an air passage in the seat. The connection duct makes the floor-side connection part and the seat-side connection part communicate with each other. By blowing air to a passenger from an outlet that is provided on a seat surface, the seat air-conditioning duct can rapidly makes the passenger feel comfortable (for example, refer Patent Literature 1).